Ziegler-Natta catalyst systems may be formed from the combination of a metal component (e.g., a catalyst precursor) with one or more additional components, such as a catalyst support, a cocatalyst and/or one or more electron donors, for example.
An example of a Ziegler-Natta catalyst includes a metal component represented by the formula:MRAx;wherein M is a transition metal, RA is a halogen, an alkoxy or a hydrocarboxyl group and x is the valence of the transition metal. For example, x may be from 1 to 4. Such a catalyst system may be used to form polyolefin compositions.